7. the height of a sunflower plant varies directly with its age. once it has sprouted from the ground, when a sunflower is 2 week old, it is 38 centimeters tall. when it is 6 weeks old, it is 114 centimeters tall. how tall is a sunflower plant that is 3 1/2 weeks old?

66.5 centimeters.

Step-by-step explanation:

We have been given that the height of a sunflower plant varies directly with its age.

Since a directly proportional equation is in form: , where k is constant of proportionality.

We are told that when a sunflower is 2 week old, it is 38 centimeters tall. Let us find constant of proportionality with given information.

We are also told that when sunflower is 6 weeks old, it is 114 centimeters tall.

We can see that constant of proportionality is 19. Let us substitute k=19 and x= 3.5 in our proportional equation to find the height of plant after 3.5 weeks.

Therefore, the sunflower plant will be 66.5 centimeters tall after 3.5 weeks.